In recent years, various biosensors have been studied and developed, and have been used in the field of medical services, drug discovery, clinical inspections, and the like. Such a biosensor recognizes external information (e.g., chemical elements) as a certain physical signal by utilizing the excellent molecule identification ability of an organism, and thus, involves various principles and objects to be measured. More specifically, the biosensor is one type of chemical sensor having a chemical substance as an object to be measured, and is composed of a molecule identification element that recognizes only an object substance to be measured, and a signal conversion element that converts the recognized information into a physical signal such as an electrical signal. In general, the molecule identification element uses a biomolecule such as enzyme, antibody, DNA, cell or microorganism, or a compound that captures such a biomolecule, and thus it is referred to as a “biosensor.”
Moreover, as a signal conversion element, a common electronic device or chemical sensor, such as an electrode, a thermistor, a quartz crystal, surface plasmon resonance or a semiconductor element, is used. Recently, a biosensor, in which a field effect transistor (FET) is used, has been vigorously studied. In the biosensor using FET, when the molecule identification element recognizes a chemical substance that is an object to be measured, a physical change such as heat, mass and electric charge, or a chemical change such as decomposition of an object substance and generation of a substance occurs. The change is converted into an electrical signal by FET serving as a signal conversion element, and the object substance is measured. The biosensor using FET has the following characteristics: (1) it can electrically detect an electric charge that is specific to an ion or a molecule; (2) it does not need time and effort before measurement; (3) it enables a real-time measurement; (4) it enables a non-labeled, non-invasive electrical measurement; and (5) it enables miniaturization and integration according to a microfabrication technique for semiconductors.
A technique of applying such a biosensor using FET to a method for non-invasively analyzing living cells has been proposed (see, for example, Patent Literature 1). This biosensor described in Patent Literature 1 has a structure in which a detection surface for detecting a change in physical properties such as a negative charge is coated with a phenylboronic acid group binding to a sialic acid sample (a cell itself or a sugar chain derived from the cell). It is considered that this biosensor is able to provide: a non-invasive, easily usable real-time cytoscreening tool that does not use a label such as a fluorescence, which has been impossible by conventional sugar chain analysis methods; and a method of detecting the sugar chain of a cell of interest by using the real-time cytoscreening tool.